For example, in this JEEP concept car, four wheels can turn in different directions, not to mention turning and spinning in the same place. But this kind of design is definitely more complicated, with higher cost, and the later maintenance cost will also increase.
Front wheel steering seems to have formed one of people's inherent impressions of cars. The patented technology of Citroen rear wheel follow-up steering, which is widely spread, is actually not a black technology. Prior to this, the vehicle has been able to achieve multi-wheel steering at the same time, but when it is applied to off-road vehicles, the early structure is complicated and cumbersome. Citroen's patented scheme is simpler, and it pioneered the use of rear wheel steering technology in passenger cars. There are many benefits of rear wheel steering, which not only improves the ground adhesion, reduces the roll, reduces the steering radius, and makes the vehicle more flexible.
At present, the mainstream rear wheel follow-up steering technology can be divided into active and passive.
I think it is more appropriate to call it four-wheel active steering, because these four wheels really take the initiative to change direction and participate in steering.
This control strategy is based on the speed of the car. When turning at low speed, the rear wheel and the front wheel turn in the opposite direction, which makes the car tend to spin in the same place and turn more sensitively and quickly.
But it can't be controlled like this at high speed, otherwise it will easily lead to out of control. At this time, the rear wheel and the front wheel turn in the same direction, which is suitable for high-speed merging, and the rear of the car follows the front of the car, which can reduce the lateral force of the car body when changing lanes and increase the stability.
Passive passive rear wheel follow-up steering is to slightly deflect the rear wheel by pressing the deformation of the bushing through the suspension system when turning, so as to improve the flexibility of cornering. For example, everyone said that the rear wheel of the old Fukang followed the steering.
In fact, the rear wheel follow-up steering technology has existed for a long time, but the design is relatively complicated and the applicable conditions are limited, which is not cost-effective compared with the increased design and maintenance costs. In addition, the current turning mode is enough to meet the needs of cars, so there is no need to make such a design, so only a few cars are equipped with this system now, on the one hand, it can really improve some dynamic performance of cars. On the other hand, it also improves the technical level of vehicles.